The present invention relates to a high voltage feedthrough and more particularly relates to a high voltage feedthrough for non-thermal plasma reactors.
Non-thermal plasma (NTP) reactors have been shown to be effective at reducing NOx emissions from diesel engines to new legislated levels. It is necessary to connect a high voltage feedthrough from the power source through the NTP reactor package to the high voltage connection on the NTP reactor. Characteristics desired in the high voltage feedthrough include the capability to: 1) pass high voltage from the input cable to the reactor without leakage of current to the housing or peripheral parts; 2) provide connections that are extremely long lasting; 3) minimize electrical noise effects; 4) provide a gas tight seal so that untreated emissions can""t escape; and 5) be low cost.
Many connector designs are known in the electrical industry. However, these designs lack compliant contact and hermetic sealing capability, two important features for NTP reactors. For example, the side wire may be removed from standard spark plugs to arrive at a possible feedthrough device, but the resultant device lacks dielectric shielding capability to prevent arcing of the center electrode to the housing and does not provide compliant contact. Such modified spark plug-insulator bodies do not extend far enough to preclude arcing. In such a device, the electrode end is flat, causing line or point contact with orientation variation. High voltage electrical feedthrough devices known in the art for radios, etc., lack hermetic sealing capability.
What is needed in the art is a high voltage feedthrough for NTP reactors providing improved dielectric shielding, longevity, minimal noise, hermetic sealing, compliant contact, ease of assembly and low cost characteristics.
High voltage feedthrough connectors in accordance with the present invention provide a durable, gas tight electrical connection from an external power source to a high voltage electrode of a NTP reactor. The connectors provide a means for isolating high voltage through a reactor housing while providing thermal expansion tolerance along with ease of assembly. The connectors comprise an insulating body having a bore of substantially single inner diameter extending axially therethrough; a center conductor disposed within said bore and comprising a first end and a second end, said first end of said center conductor having a top terminal connector for providing electrical connection to a high voltage supply and said second end of said center conductor having a bottom terminal connector for providing electrical connection to a high voltage electrode of a NTP reactor; a gas tight seal for preventing gas leaks to said center conductor; and a threaded shell assembly for engaging and connecting the insulating body-center conductor to a NTP reactor housing. The insulating body extends a sufficient distance from the threaded shell assembly and the NTP reactor housing to prevent arcing between the center conductor and the threaded shell assembly or the NTP reactor housing.
In one embodiment, a fixed center conductor provides a highly simplified design without the use of springs. In a preferred embodiment, the bottom terminal connector comprises a dome shaped tip that provides improved contact with the NTP reactor high voltage electrode and compensates for alignment variation in the NTP reactor assembly. In another embodiment, a compression spring disposed on the bottom terminal connector provides compliant contact and electrical connection to the NTP reactor high voltage electrode.
An embodiment comprising a movable center conductor provides a compression spring disposed within the bore of the insulating body in movable contacting engagement with the center conductor. In the spring-loaded embodiments, the insulating body forms an integral spring collar guide-dielectric barrier skirt thus combining spring alignment and compliant contact functions for a simplified, low cost design. If desired, a button electrode may be used.
The present high voltage feedthrough connectors afford the advantages of a simplified assembly that can be accomplished all from one side of the hex nut. The connectors can be readily applied to different reactor configurations with similar ease of assembly. One embodiment provides a combination of top down and bottom assembly. Another embodiment provides a substantially top down assembly.
The present high voltage feedthrough connectors compensate for manufacturing tolerances and thermal expansion of the reactor while maintaining adequate arcing resistance. The connectors combine formerly discrete pieces, thus reducing overall cost. The substantially single inner diameter of the bore of insulating body (excepting the threaded top section) further contributes to the overall low cost of the present high voltage feedthrough. The channel-guided spring design inhibits arcing, provides improved longevity, low manufacturing cost, and hermetic, automotive-type connections.